Xerographic fusing system



April 1969 J. B. BAKER 3,437,407

' XEROGRAPHIC FUSING SYSTEM Filed March 28, 1966 Sheet of 2 INVENTOR. JAM ES B. BAKER A 7'TOR/VEY April 8, 1969 J. B. BAKER XEROGRAPHIC FUSING SYSTEM Sheet Filed March -28. 1966 TtEi R .E u RK N .W\| h mm 053 N& 15:52 w 7 A J .8: q QUE EwV @wsw mi Tm A) 1 kg Y mumxlmmw %Bk \muw B 1% :am n 1 T: W 3 In whim Rim n mun 26 m E I My qwiw to w Q m uwiw mmiw Swim 80w Y Kim m-T -2 SEQ j IL l $5M 5m r XNQR Tam T20 ATTORNEY United States Patent 3,437,407 XEROGRAPHIC FUSING SYSTEM James B. Baker, Canandaigua, N.Y., assignor to Xerox Corporation, Rochester, N.Y., a corporation of New York Filed Mar. 28, 1966, Ser. No. 537,905 Int. Cl. G03g /00, 15/20 US. Cl. 355-3 2 Claims ABSTRACT OF THE DISCLOSURE This invention relates to an improved fusing system and particularly to an improved circuit for actuating the fusing system.

Although this invention is considered to have general application, it is particularly useful in the field of xerography and has an important application in the fusing of resinous powder images produced by electrostatography or xerography onto sheets of paper and the like to which the powder images have been transferred after they have been formed by deposition of powder on an electrostatic latent image. Therefore, for convenience of illustration the invention is described with reference to its use as a heat fuser for xerographic powder images.

In Mayo et al. Patent 3,062,109, issued Nov. 6, 1962, there is shown an electrostatic reproducing machine wherein a xerographic plate comprising a layer of photoconductive insulating material on a conductive backing is given a uniform electric charge over its surface and then exposed to the subject matter to be reproduced usually by conventional projection techniques. This exposure discharges the plate areas in accordance with the radiation intensity that reaches them and thereby creates an electrostatic latent image on or in the plate coating. The image is then developed on the plate and transferred to support material, usually paper.

As the art of xerography has progressed, it has been found preferable to develop line copy images with a powder or toner formed of any of a variety of pigmented thermoplastic resins that have been specifically developed for the purpose. These developing materials are specifically compounded for producing dense images of high resolution and to have characteristics to permit convenient storage and handling. Such developing materials are compounded to permit them to be fixed to the surface of a transfer material by heat fixing techniques. The individual particles of resin (toner) soften and coalesce when heated so that they become sticky and readily adhere to the surface of the transfer material.

One of the important applications of the process of xerography comprises its use in high speed automatic copying machines for general use wherein the powder images formed on a xerographic plate are transferred to cut sheet paper and then fixed thereon by heat fusing. In order to fuse resinous powder images formed of the powdered resins now commonly used, it is necessary to heat the powder and the paper to which it is to be fused to a relatively high temperature, such as approximately 325 F. It is undesirable, however, to raise the temperature of the paper substantially higher than 325 F. because of the tendency of paper to discolor at such elevated temperatures.

With the advent of higher speed xerographic machines, it is necessary to provide a minimum amount of warm up time when the machine is first turned on and also a minimum amount of warm up time when the machine is used subsequent thereto. For example, when the machine is first activated at the beginning of a day, or after having shut down for a long period of time, the main heating elements are activated and in addition a supplementary heating coil here is also activated in order to ready the fusing system for operation in the minimum time. This requires a certain warm up time before the scanning mechanism can be activated and thus produce a fused copy. The supplemental coil is then inactivated. After this warm up period, the scanning mechanism is activated and paper is passed through the transport under the fuser and all the image areas are fused.

After a series of copies is made, the machine starts its time-out cycle. The scanning mechanism and fuser are then shut down. It is then necessary to have a system and a circuit such that the machine may be reactivated when a copy is desired to be produced with the least possible delay but still allowing a proper warm up time for the fuser to reach the proper temperature.

It is therefore an object of this invention to improve fusing systems such that fused xerographic copies are produced under all conditions with a minimum amount of delay between initial and subsequent startups.

Another object of this invention is to improve the circuit for activating a fusing system within a xerographic machine that is easy to operate, install and inexpensive to produce.

A still further object of this invention is to de-energize the supplemental heating coil in a fusing system in the minimum time period required while still allowing the fuser to warm up to operating temperature.

These and other objects of the invention are attained by means of a fusing device that thas main heating elements and at least one supplemental heating element. The circuit includes a pair of timers to cause de-energization of the supplemental element or elements in the minimum time required for the fuser to warm up to operating temperature.

For a better understanding of the invention as well as further objects and features thereof reference is had to the following detailed description of the invention to be read in connection with accompanying drawings:

FIG. 1 is a schematic view of a preferred embodiment of the xerographic apparatus used with the present invention; and,

FIG. 2 is a schematic electrical circuit wiring diagram incorporating the present invention.

As showin in FIGURE 1, the xerographic apparatus comprises a xerographic plate including a photoconductive layer or light receiving surface on a conductive backing and formed in the shape of a drum 20' which is journaled in a frame to rotate in the direction indicated by the arrow to cause the drum surface sequentially to pass a plurality of xerographic processing stations.

For the purpose of the present disclosure, the several xerographic processing stations in the path of movement of the drum surface may be described functionally as follows:

A charging station at which a uniform electrostatic charge is deposited on the photoconductive layer of the xerographic drum is shown at A. An exposure station at which a light to be reproduced is projected onto the drum surface to dissipate the drum charge on the exposed areas thereof, and thereby form a latent electrostatic image on the copy to be reproduced is shown at B. A developing station, where a xerographic drum is developed is shown at C. A transfer station at which the xerographic powder image is electrostatically transferred from the drum surface to the material is shown at D. A drum cleaning station is shown at E.

The charging apparatus or corona charging device 22 includes a corona discharge array of one or more discharge electrodes that extend transversely across the drum surface and are energized from a high potential source and are substantially enclosed within a shielding member.

The optical scanning or projection assembly generally designated 24, comprises a copyboard or platen 60 which may consist of a transparent plate member which is adapted to receive an original. The copyboard is uniformly illuminate-d and arranged in light projecting relation to the moving light receiving surface of the xerographic drum.

Adjacent to the exposure station is a developing station C in which there is positioned a developer apparatus 26 including a developer housing having a lower or sump portion for accumulating developer material 30. Mounted within the developer housing is a motor driven buckettype conveyor used to carry the developer material previously supplied to the developer housing to the upper portion of the developer housing from where the developer material is cascaded over a hopper chute onto the drum.

As the developer material cascades over the drum, toner particles of the developer material adhere electrostatically to the previously formed electrostatic latent image areas on the drum to form a visible xerographic powder image; the remaining developer material falling off the peripheral surface of the drum into the bottom of the developer housing. Toner particles consumed duringthe developing operation to form the xerographic powder images are replenished by a toner dispenser 28 mounted within the developer housing.

Positioned next adjacent to the developing station is the image transfer station D which includes a suitable sheet feeding mechanism adapted to feed sheets of paper successively to the xerographic drum in coordination with the presentation of the developed image on the drum at the transfer station.

The next and final station in the device is a drum cleaning station E whereat any powder remaining on the xerographic drum after the transfer step is removed and whereat the xerographic drum is flooded with light to cause dissipation of any residual electrical charge remaining on the xerographic drum.

Removal of residual powder from the xerographic drum is effected by means of a brush cleaning device 46 adapted to continuously clean the xerographic drum.

From the transfer station D the image-bearing sheet is transported beneath heat fuser 50 whereby the developed and transferred xerographic powder image on the sheet is permanently fixed thereto. The heat fuser is one of the type disclosed in Eichler 2,965,868 issued Dec. 20, 1960. In the instant embodiment the heat fuser is shown having seven elements rather than the five disclosed in the aboveidentified patent. The purpose of these elements will be described hereinafter.

It is believed that the foregoing description is suflicient for the purposes of this application to show the general operation of the xerographic reproducing apparatus. For further details concerning the specific construction of the xerographic apparatus shown, reference is made to the above-mentioned Patent No. 3,062,109 issued Nov. 6, 1962 to Mayo et al.

A circuit shown in FIG. 2 is provided for initiating operation of the fusing system. The resistance elements R1 and R2 represent the elements in the fuser. In the instant embodiment the resistance R1 represents six normally on elements while the resistance R2 represents the supplemental heating element.

When the machine is installed, a determination is made as to the voltage leading to the circuit that initiates the system. This is indicated on the drawing as between 107 and 125 volts. The lead lines to the resistance heating 4 elements R1 and R2 are thus connected as desired to the leads indicated as 109 volts, 112 volts, 115 volts, 118 volts, 121 volts, 124 volts through the transformer T-2. Thus depending on what the voltage leading to the machine is, the lead lines to the resistances can be adjusted to obtain the desirable range thereby providing for any variation in the line voltage.

For purposes of illustration, the description below will be divided into three categories that of initial starts, subsequent running starts, and subsequent starts.

An initial start is one that occurs, for example, at the beginning of a day or after the machine has been turned off for a long period of time. A subsequent running start is one wherein the print button is activated when the machine is still running. Subsequent starts are ones wherein the machine is activated at a point subsequent to the cycling out of the machine and one in which the machine has not cooled down sufiiciently such that the condition would be that of an initial start.

The fusing system is provided with a series of 5 switches SW-8A, SW-8B, SW-8C, SW3A, SW-3B as indicated in FIG. 2. These switches appear to the operator as 1, 2, 3, high and low. The switches are either in the 1, 2, or 3 position and either the high or low position thus giving a variation of six different fusing levels. When any one of the switches 1, 2, or 3 is actuated the other 2 are cammed out of operation. Likewise when either the high or low switch is actuated the other is cammed out of operation. For example as shown in FIG. 2, switch 2 and the low switch are shown actuated, thus the voltage across R1 is 112 volts. If in the above example, the high switch rather than the low switch was actuated by the operator the coils R2 would have remained in operation after the pre-heating cycle described below.

For an initial start, the operator pushes the start button or switch SW-l which is on the control panel marked on. This activated control relay 1CR which closes its own holding contacts 1CR-3 and maintains this relay closed. Contacts 1CR-2 are also closed energizing transformer T-2 thereby providing power to the fuser and actuating 6TR, R1 and R2 as shown in FIG. 2. Contacts 1CR1 are also closed energizing timer 2TR. Timers 2TR and 6TR are thermal delay timers located in the circuit and have a resistance element adjacent to a bimetal strip which bears the movable contact point. At the rated voltage, the timers have an initial cycling time of 20 seconds and 2 seconds respectively. Thus after the time of two seconds has elapsed the contacts 6TR are closed, the bimetal strip heats up and closes the contacts. This provides time for other purposes such as the lamps warming up before ignition.

As 6TR warms up for 2 seconds and 6TR contacts are closed, ZTR warms up for 20 seconds and 2TR contacts close. During this period of time since 1CR is closed, the fusing elements R1 and R2 are heating up. As the 2TR is actuated in 20 seconds and 2TR contacts close, 2CR and 7CR coils are actuated thereby closing 2CR2 contacts which actuates the solenoid SOL-4 and 3CR coil when print switch SW-7 is pushed, which in turn actuates the scanning mechanism, the main drive mechanism, and the paper feed mechanism 3CR closes its own holding contacts 3CR-A and maintains this relay closed and opens 3CR-B contacts. 2CR-1 contacts are opened removing volts from 6TR coils allowing this coil to cool down and open 6TR contacts. 7CR coil actuates and opens 7CR-1 contacts and closes 7CR-2A contacts. The contacts 7CR-2A hold 7CR and ZCR coils actuated. 7CR-1 contacts open which removes voltage from R2 the supplemental pre-heat fusing elements unless the machine is in the high position on switch SW-3B.

For subsequent running starts, assuming that 2TR has not cooled down sufiiciently to allow 2TR contacts to open or if the machine is still running, but not copying the print button may be pushed with the result described below. Since 6TR has been out of the circuitry for the length of time that the machine was previously running (when 2CR-1 was opened) this timer, less the 20 seconds for the machine to warm up, has cooled down enough such that it will require 2 seconds to warm up before 7CR and ZCR coils can be actuated and the machine subsequently started.

If on the other hand, the operator wishes to make an additional copy after the machine has cycled out he will push the on button and the print button. In such a case if the machine has not cooled down completely such that the thermal delay timer ZTR is in the condition of an initial start, the machine will commence operation in between 2 seconds, as in a subsequent running start condition and 20 seconds as in an initial start condition.

This time to start the machine will depend on how long the machine has been cooled down or how long it will take the fuser to sufiiciently heat up so that fused copies can be produced. When the machine shuts down, 2TR will cool down according to the length of time the machine has been off. A suitable timer is thus provided for this purpose which cools down at a rate similar to that rate at which the fuser cools down. Therefore, since ZTR has been out of circuitry the length of time that the machine has cycled out, it has cooled down to a certain extent and can now be actuated anywhere from 2 seconds as in the subsequent running start condition to 20 seconds when the timer is completely cooled down in the initial start condition.

When lCR-l was energized the on button was actuated and lCR was closed, a third timer 3TR-MOT was energized. This is a 50 second motor driven timer and opens the contacts 3TR in that period of time. If the on button is pushed and the machine warms up for the given 20 seconds and the print button is not pushed the 50 second period allowed for the 3TR timer, the contacts STR will open and the machine will automatically shut down. If on the other hand, the print button is pushed prior to the 50 second period the relay 3CR is energized thereby closing the contacts 3CR-A providing its own circuit and opening the contacts 3CR-B thereby cutting 01f the voltage to 3TR. When the last copy is made as indicated by the programmer built in to the machine and fully described in the above-entitled Patent 3,062,109

' the contacts 5CR are opened thereby de-activating relay 3CR opening the contacts 3CR-A and closing the contacts 3CR-B thereby activating the timer 3TR for 50 seconds which in that period of time will open the contacts 3TR thereby shutting down the machine.

It will be understood that various changes in the details, materials, steps and arrangements of parts, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims. However, while the invention has been described with reference to the structure disclosed herein, it is not to be confined to the details set forth, and this application is intended to cover such modifications or changes as may come within the scope of the following claims.

What is claimed is: 1. A Xerographic reproducing apparatus having a fusing system for fixing fusible powder images on a support surface, a main electrical circuit for energizing the apparatus and the fusing system and a control element in the circuit for controlling xerographic processing of the apparatus, said fusing system including a fusing device having at least one main heater element and at least one supplemental heating element,

said system including a fuser control circuit connected between the main circuit and fusing device for normally supplying electrical power to the heater elements,

said control circuit having a pair of switches arranged to control de-energization of the supplemental heater element when the switches are in one controlling condition,

said control circuit including a first delay timer operable upon one of said switches to place the same in said controlling condition after a first period of time and a second thermal delay timer operable upon the other of said switches to place the same in said controlling condition after a second period of time thereby causing de-energization of said supplemental heater.

2. A Xerographic reproducing apparatus as in claim 1 wherein said switches are associated with the control element and operable when placed in said controlling condition to actuate said control element for causing operation of the xerographic apparatus.

References Cited UNITED STATES PATENTS JOHN M. HORAN, Primary Examiner. 

